nghttpx: Don't re-enter offline if it is already in offline mode

src/shrpx_connect_blocker.cc

@@ -35,7 +35,7 @@ void connect_blocker_cb(struct ev_loop *loop, ev_timer *w, int revents) {
 } // namespace
 
 ConnectBlocker::ConnectBlocker(std::mt19937 &gen, struct ev_loop *loop)
-    : gen_(gen), loop_(loop), fail_count_(0) {
+    : gen_(gen), loop_(loop), fail_count_(0), offline_(false) {
   ev_timer_init(&timer_, connect_blocker_cb, 0., 0.);
 }
 
@@ -81,6 +81,12 @@ void ConnectBlocker::on_failure() {
 size_t ConnectBlocker::get_fail_count() const { return fail_count_; }
 
 void ConnectBlocker::offline() {
+  if (offline_) {
+    return;
+  }
+
+  offline_ = true;
+
   ev_timer_stop(loop_, &timer_);
   ev_timer_set(&timer_, std::numeric_limits<double>::max(), 0.);
   ev_timer_start(loop_, &timer_);
@@ -90,6 +96,10 @@ void ConnectBlocker::online() {
   ev_timer_stop(loop_, &timer_);
 
   fail_count_ = 0;
+
+  offline_ = false;
 }
 
+bool ConnectBlocker::in_offline() const { return offline_; }
+
 } // namespace shrpx

src/shrpx_connect_blocker.h

@@ -57,6 +57,9 @@ public:
   // Peer is now considered online
   void online();
 
+  // Returns true if peer is considered offline.
+  bool in_offline() const;
+
 private:
   std::mt19937 gen_;
   ev_timer timer_;
@@ -64,6 +67,8 @@ private:
   // The number of consecutive connection failure.  Reset to 0 on
   // success.
   size_t fail_count_;
+  // true if peer is considered offline.
+  bool offline_;
 };
 
 } // namespace

src/shrpx_worker.cc

@@ -478,6 +478,10 @@ size_t match_downstream_addr_group(
 void downstream_failure(DownstreamAddr *addr) {
   const auto &connect_blocker = addr->connect_blocker;
 
+  if (connect_blocker->in_offline()) {
+    return;
+  }
+
   connect_blocker->on_failure();
 
   if (addr->fall == 0) {